Administration of 100% oxygen in diving accidents - an evaluation of four emergency oxygen devices

As the use of oxygen enhances the resorption of gas bubbles in decompressio n illness, it is recommended and generally accepted that the inspired oxyge n concentration in emergency treatment of diving accidents has to be as clo se to 100% as possible. Therefore, several emergency oxygen devices are off ered to the diving community but only with little data in literature on the efficacy of these devices. We tested four emergency oxygen devices with re spect to efficacy of oxygen supply and breathing comfort at rest. Nine blin ded volunteers had to breathe from the four systems with face mask and mout hpiece as well. Gases were measured with mass spectrometry during a 3 min i nterval from a capillary port close to the subject. The results showed that none of the systems was able to deliver 100% oxygen all the time, but in t hree systems inspiratory oxygen values were achieved, although in one syste m the nitrogen wash-out was slowed due to air contamination during inspirat ion. The fourth tested system frequently supplied the subjects simply with air while breathing at rest. We conclude from our study that it is difficul t to achieve oxygen levels close to 100% in practice. Even in a perfectly w orking system, the interface between device and subject is a source of entr ained air, especially when oxygen breathing has to be performed over a long er period of time. In addition, two of four systems had conceptional proble ms to supply the subjects with pure O-2 during inspiration. None of the tes ted systems was perfectly designed to serve in such emergencies.